1. Prior Art
The prior art is believed to be exemplified by the following:
Dreyfus; U.S. Pat. No. 2,086,701; 7/37 PA0 Burns; U.S. Pat. No. 2,233,243; 2/41 PA0 Kroyer; U.S. Pat. No. 2,954,304; 7/57 PA0 Graham; U.S. Pat. No. 3,692,530; 9/72 PA0 Funk et al; U.S. Pat. No. 3,523,911; 8/70 PA0 Ramos-Rodriguez; U.S. Pat. No. 3,701,789; 10/72 PA0 Jaffe et al; U.S. Pat. No. 3,784,408; 1/74 PA0 Algeo; U.S. Pat. No. 3,817,786; 6/74 PA0 Knauth; U.S. Pat. No. 4,023,982; 5/77 PA0 Kiminki et al; U.S. Pat. No. 4,029,515; 6/77 PA0 Fann; U.S. Pat. No. 4,072,538; 2/78 PA0 483,431 (Russia) 12/75 PA0 Dunning et al, "The Saccharification of Agricultural Residues", Industrial and Engineering Chemistry, pp. 24-29, January, 1945. PA0 Church et al, U.S. patent application Ser. No. 2,885 filed 1/12/79--"Continuous Process for Cellulose Saccharification"; PA0 Faber et al, U.S. patent application Ser. No. 053,979 filed 7/2/79--"Fermentable Acid Hydrolyzates and Fermentation Process". PA0 Burroughs et al, Ser. No. 2,886 filed 1/12/79--"Reactor System and Pump Apparatus Therein".
2. Field of the Invention
It is now known that lignocellulosic constituents of used wood, paper and agricultural byproducts such as sawdust, newspaper, corncobs, straw, sugar cane bagasse, etc. may be converted into hydrolyzates suitable for use as the raw fermentable substance to convert sugar into ethyl alcohol.
With the advent of gasohol and the increasing need for alternatives to petroleum based fuels, there is an increasing need for methods by which abundant and renewable resources may be converted into alternative fuels.
In U.S. application Ser. No. 2,885 filed Jan. 12, 1979 of Church et al entitled "Continuous Process For Cellulose Saccharification" and commonly assigned herewith, there is described a method and apparatus for saccharification of cellulosic products in which the polysaccharide constituents of typical waste products may be converted into glucose and either furfural or xylose. Such a process conveniently, rapidly and economically provides by acid cellulose hydrolysis, a hydrolyzate which contains glucose fermentable to ethanol.
Although such method has been made available for conversion of cellulosic materials, no similar advances have heretofore been made for the like conversion of whole starchy materials.
Starchy materials have heretofore been converted to sugars by acid hydrolysis or by enzymatic action. For example, corn syrup is conventionally produced by acid hydrolysis. However, in such conventional processes, it is customary to first separate out the non-starchy components of the corn and employ only pure starch as a reactant to avoid a deleterious browning effect caused by the well known Maillard reaction which arises when glucose is acted upon by acid in the presence of protein. Acid hydrolysis of pure starch is known to produce good yields in both batch and continuous processes but, because of the inability to use other than pure starch starting material, the method lacks versatility and is expensive. Even when pure starch is the starting material, known acid hydrolysis technology cannot produce a glucose yield of better than 88% when starch concentrations of around 20% are used. The glucose loss in this case is not due to the Maillard reaction, as no amino acids are present, but rather to the acid-catalyzed reversion and degradation reactions of the glucose. Nearly theoretical yields can be obtained at very low starch concentrations; however use of such low concentrations is commercially impractical due to high dilution of the glucose.
Starch has also been hydrolyzed by an enzymatic method wherein whole grain or pure starch is converted to corn syrup, crystalline glucose or fermentable sugars by enzyme action in batch processes. Such methods result in high yields and provide versatility in terms of suitable starting materials. However, such methods suffer from the disadvantage of being extremely slow, requiring anywhere from 1 to 4 days per reaction cycle. Moreover, such methods require the extra expense of separate and complex equipment for enzyme generation or processing necessitating large and elaborate plants.
It is an object of this invention to provide rapid, efficient and economical means for converting starchy materials to glucose.
Another object of the invention is to provide a versatile process in that low-quality grain and/or readily accessible agricultural starchy materials may be employed without preliminary processing to isolate pure starch.
Yet another object of the invention is to provide a method for rapidly and efficiently producing fermentable sugars from readily available low-quality grain or other starchy materials, which sugars may be produced employing the same apparatus previously employed to convert cellulosic material to fermentable sugars.
These and others objects of the invention will be apparent from the description of the invention which follows.